Practical question 1

Question 1

Scatchard plot

Answer 1

X axis: B (specific binding)
Y axis: B/[D]
Gradient = -ka
X intercept = Bmax

Question 2

Specific binding

Answer 2

Total binding (excess of radioligand) - nonspecific (radioligand when excess of cold unlabelled ligand has displaced specifically bound radioligand)

Question 3

Alpha (fractional occupancy equations)

Answer 3

alpha = B/Bmax

alpha = [D]Ka / [D]ka +1

Question 4

What does Bmax mean in terms of number of receptors

Answer 4

Multiply by Avogadro’s number and the %weight or whatever question says

Question 5

Indirect binding assay/Cheng Prussov

Answer 5

X axis: log[U] i.e unlabelled competitive ligand
Y axis: X (bound radioligand)

IC50 = conc of [U] that causes 50% displacement of radioligand from specific binding sites

Question 6

Working out Ku (in indirect binding assay)

Answer 6

Ku = 1 + [L]Kl / IC50

Question 7

If competing ligand and radioligand are the same what is the Ka (for both of them)

Answer 7

Ka = 1 / IC50 - [L]

Question 8

Functional assay

Answer 8

X axis = log[agonist]
Y axis = % response

D1 = conc of agonist needed for certain % maximal response

Question 9

Dose ratio

Answer 9

DR = [D]2/[D]1 = 1 + [antagonist]K2

Question 10

Working out K2 (i.e Ka of antagonist)

Answer 10

Dose ratio -1 / [antagonist]